1. Field of the Invention
The present invention relates to a bow-formed bumper for a vehicle and a method of forming the bow-formed bumper. The method of forming the bow-formed bumper may comprise hydroforming the bow-formed bumper.
The present invention further relates to a method of hydroforming a blank with a closed profile in a partible tool by supplying a pressure fluid into the blank.
2. Background Information
Hydroforming is a well-known forming process that uses pressurized fluid, such as water or oil, or, less commonly, pressurized gas to deform a structural member into a desired shape. Generally in this process, the structural member is placed inside a die, usually made of two die sections that are placed about the structural member. The inside of the die determines the shape of the product to be formed. The structural member is then filled with the pressurized fluid. The pressure of the fluid is such that the structural member is outwardly deformed into conformance with the shape of the interior of the die to create the desired shape. This is especially useful in creating substantially tubular or box-shaped beams or other structural pieces for use in vehicles.
This well known technique is limited substantially to steels with a good formability. Steel with a high yield strength has too limited elongation and can therefore only be used when the forming is light. It is, however, conventional to hydroform in several steps and to anneal between the forming steps when greater forming is desired than the steel itself permits.